1. Field of the Invention
The present invention relates to a method of controlling individual pixels in a display formed of a plurality of pixels wherein a frequency mixing system is employed to control individual pixels in the display.
2. State of the Art
Digital systems have been used to control displays formed from a plurality of pixels. Such displays range from relatively small screens as used on digital equipment such as lap top and notebook computers to large displays used in outdoor signs. In conventional digital control systems, gray scale is implemented by adjusting the logical "ON" time for each pixel according to brightness (brighter pixels are simply turned on longer than pixels that are not as bright). This division of time for controlling brightness results in a high digital bandwidth for the computer controlling the display.
In addition, digital systems must use a complex system of timing for turning pixels on and off inasmuch as two pixels occurring in a different row or column cannot be turned on simultaneously without inadvertently turning on two additional pixels that are not intended to be turned on. FIG. 1 of the drawings shows what happens when a digital system attempts to turn two pixels on at the same time when the two pixels are in a different column or row. In the array shown in FIG. 1, say it is desired to turn on pixels 3 and 8. If a digital system is being used to control the display, a pixel will be on when the column in which it resides is high and the row in which it resides is low. Thus, to turn on pixel 3, column 1 must be high and row 3 must be low. Now, if it is attempted to simultaneously turn pixel 8 on, column 3 must be made high and row 2 must be made low. Unfortunately, as can be seen, when this is done, pixels 2 and 9 are turned on in addition to the intended pixels 3 and 8. Pixels in different rows and columns thus need to be controlled individually, i.e., be turned on and off separately.
To turn each pixel on separately from other pixels while adjusting gray scale and running 10 to 30 frames per second on the display requires a broad bandwidth on the computer which is being used to control the display. For a display having 3000 pixels, with a gray scale of 256 and the capacity to run 30 frames per second on the display, the computer required must have the capability of running at a clock speed of over 100 MHz. It would be highly desirable to provide a method of controlling individual pixels in a display that can utilize a much less powerful computer running at a clock speed of less than 10 to 20 MHz.